<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>var</title>
</head>
<body>
    

    <script>
    
        var a = 100;

        (function () {

            alert(a++);

            var a = 10;

            alert(a++);

        })();
    
    </script>

</body>
</html>